Personal Resilience in Project Management 2 - TV Edit 1a.pdf
Structure of proteins and nature of bond linking monomers in a polymer
1. STRUCTURE OF PROTEINS
Dr. Harinatha Reddy
Assistant Professor
Department of
Microbiology
Nature of bond
linking monomers in a
polymer
2. • Proteins, as mentioned earlier, are heteropolymers
containing strings of amino acids.
• Biologists describe the protein structure at four levels.
• Primary,
• Secondary,
• Tertiary,
• quaternary structure.
4. Primary structure
• The sequence of amino acids i.e., the positional
information in a protein – which is the first amino acid,
which is second, and so on – is called the primary
structure of a protein.
5. Primary structure
• A protein is imagined as a line, the left end represented
by the first amino acid and the right end represented by
the last amino acid.
• The first amino acid is also called as N-terminal amino
acid. The last amino acid is called the C-terminal amino
acid.
6. secondary structure
• A protein thread does not exist throughout as an
extended rigid rod.
• The thread is folded in the form of a helix .
• In proteins, only right handed helices are observed.
7. • Secondary structure of protein again two types:
• Alpha helix: Alpha keratin and Beta keratin protein.
• Beta plated sheet: Silk protein: Fibroin and sericin.
9. Tertiary structure of proteins
• In addition, the long protein chain is also folded upon
itself like a hollow woolen ball, giving rise to the tertiary
structure,,,
10. • Tertiary structure gives us a 3-dimensional view of a
protein.
• Tertiary structure is absolutely necessary for the many
biological activities of proteins
11. Quaternary structure of a protein
• Some proteins are an assembly of more than one
polypeptide or subunits.
• These individual folded polypeptides or subunits are
arranged with respect to each other (e.g. linear string of
spheres, spheres arranged one upon each other in the
form of a cube or plate etc
12. • Adult human haemoglobin consists of 4 subunits.
• Two of these are identical to each other.
• Hence, two subunits of α type and two subunits of β
type together constitute the human haemoglobin (Hb).
13. Nature of bond
linking monomers in a polymer
• Proteins:
• Polysaccharides:
• Nucleic acids (DNA, RNA)…
14. Peptide bond in proteins:
• In a polypeptide or a protein, amino acids are linked by
a peptide bond.
15. • Peptide bond formed when the carboxyl (-COOH) group
of one amino acid reacts with the amino (-NH2 ) group
of the next amino acid ..
• During peptide bond formation water molecule is
eliminated …….(the process is called dehydration).
18. Glycosidic bond in polysaccharide
• In a polysaccharide the individual monosaccharides are
linked by a glycosidic bond.
• This bond is also formed by dehydration.
• This bond is formed between two carbon atoms of two
adjacent monosaccharides.
20. • In a nucleic acid a phosphate
moiety links the 3’-carbon of
one sugar of one nucleotide
to the 5’-carbon of the sugar
of the other nucleotide.
• The bond between the
phosphate and hydroxyl
group of sugar is an ester
bond.
• As there is one such ester
bond on either side, it is
called phosphodiester bond
21. • Nucleic acids exhibit a
wide variety of
secondary structures.
• Secondary helica
structure of DNA
proposed by Watson-
and Crick.
22. • The two strands of polynucleotides
are antiparallel i.e., run in the
opposite direction.
• The backbone is formed by the
sugar phosphate-sugar chain.
23. • The nitrogen bases are projected
more or less perpendicular to this
backbone but face inside.
• A and G of one strand compulsorily
base pairs with T and C,
respectively, on the other strand.
25. • There are two hydrogen bonds between A
and T and three hydrogen bonds between
G and C.
• At each step of ascent, the strand turns
36°.
• One full turn of the helical strand would
involve ten steps or ten base pairs.
26. • The pitch would be 34Å.
• The rise per base pair would be 3.4Å.
• This form of DNA with the above
mentioned salient features is called
BDNA.
• There are more than a dozen forms of
DNA present.